1. Field of the Invention
The present invention relates to portable database systems. More particularly, it relates to an improved method of storing databases in a portable computer and an improved method of interchanging data records between a master and a portable computer.
2. Description of Background Information
Database systems allow storing and retrieving of data records relating to critical business information, such as customer information, stock quotes and inventory availability; or to personal information, such as nutrition and road direction information. Storage space required for storing the data records varies according to the number and volume of the data records. In non-portable computers, storage space may be quite easily expanded to provide for large databases. In portable computers, due to need for portability, expansion of storage space is comparatively more constrained.
Portable computers typically refer to laptops, notebooks, Personal Digital Assistants (PDAs) and palmtop organizers. They are designed to allow users perform computing tasks and manage personal information while the users are travelling. Users can also depend on their portable computers to retrieve information from a master database residing in a master computer. For example, a travelling salesman may need to access price and stock availability for a particular product. He can make a telephone call to relay his request for information, or he can retrieve such information from a database stored in a portable computer. For the latter, a copy of the database has to be first downloaded into his portable computer—this copy of database is hereafter referred to as a “portable database”. When changes are effected at the master database or at the portable database, both the master and the portable databases need to be updated through a synchronization process to ensure the data is up-to-date.
In existing solutions, portable databases are merely replicas of the master database, containing complete data structure and all data records. While this solution ensures completeness of the portable database, a potential problem is insufficient and inefficient utilization of storage space in the portable computer. Generally, the storage capacity of memory of a portable computer is a few orders of magnitude smaller than that of a master computer. Portable computers are also usually lightweight and have small form factor to serve its purpose as a portable device, and hence are preferably not attached to bulky storage devices. Thus, in order to store a copy of a master database in the portable computer, a significant portion of the storage space of the portable computer may be needed. In some instances where there is complex data structure or large data volume, the portable computer storage may even be insufficient to store the entire master database.
To overcome insufficient storage, existing solutions propose downloading only the data fields relevant to a user's needs. While this solution significantly reduces storage needs, it still allows downloading the same number of data records, which include a potentially large number of unneeded data records.
From the foregoing, an improved method of storing databases in a portable computer and an improved method of interchanging data between a master and a portable computer are needed.